It is the goal of this research to biochemically and serologically characterize the mucoid substance produced by strains of Pseudomonas aeruginosa isolated from the respiratory tree of patients with cystic fibrosis (CF). Methods will be used to purify the mucoid antigens, characterize them chemically, produce antisera to them and develop serologic assays for assessing both antibody responses to and antigenic relationships amongst mucoid antigens. Further studies will employ a sensitive serological assay, radioactive antigen binding, to determin if any immune response occurs amongst CF patients to this antigen. Prior development of a serotyping system for mucoid antigens will allow assessment of serological responses of colonized CF patients. Use of animal sera to mucoid substances will allow us to have positive controls for these assays. Analyses of the mitogenic properties of mucoid antigens for human lymphocytes will be undertaken to determine if it is capable of interacting with these cells. These tests will look for the induction of helper or suppressor T cells by mucoid antigens in both normal persons and CF patients colonized and not colonized with mucoid P. aeruginosa as well as the response of these CF patients to serotypically homologous and heterologous mucoid antigens. Long-term objectives of this study include an understanding of the role of mucoid antigens in the immunity to mucoid P. aeruginosa, and definition of immunoregulatory phenomena associated with mucoid antigens. This proposal unites the fields of microbiology and bacterial immunochemistry with immunology in order to understand the potential role of mucoid exopolysaccharides in the pathogenesis of mucoid P. aeruginosa. These data could potentially provide a basis for assessing the vaccine potential of mucoid antigens in preventing P. aeruginosa colonization of CF patients.